Phthalocyanine compounds are useful as coatings, printing inks, catalysts or electronic materials and have recently been given extensive study particularly for their use as electrophotographic photosensitive material, optical recording materials and photoelectric conversion materials.
It is known that phthalocyanine compounds generally exhibit several different crystal forms depending on the process of production or the process of treatment and that the difference in crystal form has a great influence on their photoelectric conversion characteristics. For example, known crystal forms of copper phthalocyanine include .alpha.-, .pi.-, .chi.-, .rho.-, .gamma.-, and .delta.-forms as well as a stable .beta.-form. These crystal forms are known capable of interconversion by a mechanical strain, a sulfuric acid treatment, an organic solvent treatment, a heat treatment, and the like as described, e.g., in U.S. Pat. Nos. 2,770,629, 3,160,635, 3,708,292, and 3,357,989. Further, JP-A-50-38543 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") has a mention of the relationship between a crystal form of copper phthalocyanine and its electrophotographic sensitivity.
Besides copper phthalocyanine, it has been proposed to use various crystal forms of metal-free phthalocyanine, hydroxygallium phthalocyanine, chloroaluminum phthalocyanine, chloroindium phthalocyanine, etc. in electrophotographic photoreceptors (see JP-A-1-221459, JP-A-59-168461, and JP-A59-180566).
There are a number of reports on preparation or treatment of phthalocyanine compounds. With reference to hydroxygallium phthalocyanine, for example, a process consisting of acid pasting of chlorogallium phthalocyanine with sulfuric acid and washing with water and then with aqueous ammonia is disclosed in Bull. Soc. Chim., France, No. 23 (1962), and a process consisting of hydrolyzing chlorogallium phthalocyanine using ammonium hydroxide and pyridine is reported in Inorg. Chem., Vol. 19, p. 3131 (1980).
However, any of the phthalocyanine compounds prepared by the conventional processes is still unsatisfactory in photosensitivity, stability, etc. when used as a charge generating material in an electrophotographic photoreceptor. It has thus been demanded to develop a phthalocyanine compound having improved performance properties.